This invention relates to fluorinated supramolecular polymers comprising hydrogen bonding units leading to physical interactions between different polymer chains. The physical interactions originate from multiple hydrogen bonding interactions (supramolecular interactions) between self-complementary units capable of forming at least three non-covalent hydrogen bonds. Non-covalent hydrogen bonds are well known and are also indicated as “hydrogen bridges.” Units capable of forming at least four non-covalent hydrogen bonds in a row, i.e. quadruple hydrogen bonding units, are a specific embodiment of said self-complementary units and are abbreviated as 4H-units. Sijbesma et al. (Science 278, 1601-1604, 1997; incorporated by reference) discloses 4H-units that are based on 2-ureido-4-pyrimidones. Reference is further made to U.S. Pat. No. 6,320,018, incorporated by reference. These 2-ureido-4-pyrimidones in their turn are derived from isocytosines.
Telechelic polymers based on polysiloxanes, (Hirschberg et al., Macromolecules 32, 2696-2705, 1999, incorporated by reference), and aliphatic polyesters, poly(ethylene-co-butylene), or polyethers have been modified with 4H-units (Lange et al., J. Polym. Sci. Part A 37, 3657-3670, 1999; Folmer et al., Adv. Mater. 12, 874-878, 2000; both incorporated by reference). Reference is further made to U.S. Pat. No. 7,622,131, incorporated by reference.
Additionally, polyurethane based polymers with 4H-units as end-cappers that can be used as hot melt adhesive are disclosed in US 2004/087755.
Fluorinated polymers and fluorinated materials comprising such fluorinated polymers are known in the art and are characterized by their unique properties such as hydrophobicity, oleophobicity, low surface-energy, high gas permeability, high lubricity, and low toxicity. Unfortunately, fluorinated polymers are also characterized by difficult processing conditions (high temperatures and/or expensive fluorinated solvents) and a limited choice in mechanical properties of the related materials. Several approaches have been developed to benefit from the desired properties of fluorinated polymers in coating applications.
Cross-linkable coating compositions based on three-component systems are disclosed in U.S. Pat. No. 6,756,468, incorporated by reference. The first component comprises a mixture of partially fluorinated prepolymers which are obtained by the reaction of (per)fluoropolyether diols and the cyclic trimer of isophorone diisocyanate (IPDI) and a non-cyclic trimer of hexamethylene diisocyanate. The second component comprises a (per)fluoropolyether diol having a lower number average molecular weight than the (per)fluoropolyether diol of the first component. The third component comprises an inert organic solvent. These coatings can be chemically cross-linked in the presence of a catalyst. Consequently, these cross-linkable coatings comprise toxic isocyanates and have a limited pot-life due to the intrinsic reactivity of the isocyanate components towards the diols. Additionally, a cumbersome three-component formulation is needed to prevent undesired cross-linking. Moreover, the cross-linked coatings lack any reversible behaviour.
In another approach, fluorinated materials for antifouling and medical applications are disclosed in US 2007/254278 and US 2009/0165320, both incorporated by reference. These materials have been obtained by photo-chemical cross-linking of methacrylate-functionalised perfluoropolyethers. Although these materials are viscous liquids before cross-linking, the resulting cross-linked materials are not thermo-reversible and need initiating species and UV-radiation to obtain their material properties.
Thermoplastic multi-block-copolymers comprising alternating perfluoropolyether blocks and aromatic, aliphatic or cycloaliphatic polyester blocks are disclosed in U.S. Pat. No. 5,476,910, incorporated by reference. These polymers show thermoplastic properties due to the presence of (non-fluorinated) rigid aromatic, aliphatic or cycloaliphatic blocks and flexible perfluoropolyether blocks in the polymer chain.
Thermoplastic polyurethanes comprising perfluoropolyether blocks are disclosed in Example 1 of U.S. Pat. No. 5,508,380, incorporated by reference. These are obtained by polycondensation of perfluoropolyether diols with 4,4′-methylene diphenyl diisocyanate (MDI) and butanediol.
There is a need in the art for improved fluorinated materials that show thermally reversible properties which allow thermal processing at lower temperatures, and display self-healing properties. Additionally, the thermo-reversible nature of these improved fluorinated materials allows the use solvent-free formulations thereby making the use of, ecologically not preferred, fluorinated solvents which are typically used for manufacturing formulations and materials comprising fluorinated polymers, superfluous.
The present invention discloses fluorinated supramolecular polymers and fluorinated supramolecular materials comprising a fluorinated supramolecular polymer. The fluorinated supramolecular polymers are liquids at elevated temperatures whereas they are elastomeric at ambient temperature. Moreover, the fluorinated supramolecular polymers according to the present invention can be formulated without the need for (fluorinated) solvents. Fluorinated supramolecular materials display self-healing properties whereby autonomous repair of damaged materials takes place thereby providing a means to repair cracks and scratches autonomously. They also maintain the protective function of a coating to shield the substrate from the surrounding environment.